The long range objective of the proposed research is the development of an immunocontraceptive vaccine providing safe and effective control of human fertility. The focus of the present application is the Mr = 55,000 antigen (ZP3) of pig oocyte zona pellucida. Concerted biochemical, immunological and biological investigations will critically evaluate the contraceptive potency and mechanism of action of antibodies produced by active immunization of female rabbits with deglycosylated preparations of ZP3 alpha and ZP3 beta, the two component glycoproteins comprising the intact ZP3 antigen. Biochemical studies will examine the effects of deglycosylation on protein conformation (secondary structure) and associative properties of ZP3 alpha and ZP3 beta by optical (ultraviolet circular dichroic spectra) and chromatographic (gel filtration chromatography) means, respectively. Immunological investigations will assess the effects of deglycosylation on the antigenicity and immunogenicity of ZP3 alpha and ZP3 beta. Antibody titers will be monitored by radioimmunoassay using intact ZP3 as radiolabeled tracer. Biological investigations will examine the effects of various ZP3 antibodies on ovarian function (steroid secretion and follicular development). Rabbits will be actively immunized with ZP3, isolated ZP3 alpha and ZP3 beta, and deglycosylated preparations of ZP3 alpha and ZP3 beta. Estradiol and progesterone profiles (steroid secretion) and ovarian histology (follicular development) will be monitored over a nine month period following hCG induced pseudopregnancy at six week intervals. In addition, the various antisera will be tested for capacity to inhibit sperm-zona attachment (pig gametes) as a measure of contraceptive potency at the level of sperm-egg interaction. Antibodies which either inhibit fertility at the level of prefertilization sperm-egg interaction or exert a prefertilization anti-fertility effect at the level of the ovary (inhibition of follicular development) with the concomitant absence of endocrine perturbation would designate the corresponding modified ZP3 immunogen as a potential new contraceptive target antigen for future immunocontraceptive studies.